#include <stdio.h>
#include <unistd.h>

int main()
{
    const char message[] = "hello world\n";//自定义缓冲区
    ssize_t poi = write(1, message, sizeof(message)-1);//此处fd传的1
    if (poi == -1) {  
        perror("write");  
        return -1;
    } 

    return 0;
}